Iliohypogastric nerve

Structure

Origin

The iliohypogastric nerve originates from the superior branch of the anterior ramus of spinal nerve L1. It also receives fibers from T12 via the subcostal nerve. The branch below it is the ilioinguinal nerve.

Course

It emerges from the upper lateral border of the psoas major. It then crosses in front of the quadratus lumborum muscle to an area superior to the iliac crest. It runs behind the kidneys. Just superior to the iliac crest, it pierces the posterior part of the transversus abdominis muscle and continues anteriorly in the abdominal wall between the transversus abdominis and internal oblique muscles.

It divides into a lateral cutaneous branch and an anterior cutaneous branch between the transversus abdominis muscle and the internal oblique muscle.

Branches

Lateral cutaneous branch

The lateral cutaneous branch ("iliac branch") pierces the internal oblique muscles and the external oblique muscles immediately above the iliac crest. It is distributed to the skin of the gluteal region, behind the lateral cutaneous branch of the subcostal nerve; the size of this branch bears an inverse proportion to that of the lateral cutaneous branch of the subcostal nerve.

When harvesting bone from the anterior iliac crest (AICBG), the lateral cutaneous branch of the Iliohypogastric nerve (L1) is most likely to be injured.

Anterior cutaneous branch

The anterior cutaneous branch ("hypogastric branch") continues onward between the abdominal internal oblique and transverse muscles.

It then pierces the internal oblique, becomes cutaneous by perforating the aponeurosis of the external oblique about 2.5 cm above the subcutaneous inguinal ring, and is distributed to the skin of the hypogastric region.

Communications

The iliohypogastric nerve communicates with the subcostal nerve and ilioinguinal nerves.

Variation

The iliohypogastric nerve may be absent in up to 20% of people. Its fibres are instead carried on other nerves, such as the ilioinguinal nerve.